Conventional plate-type heaters, which generate heat when electricity is applied to them, are not only clean and do not cause air pollution, but their temperature can easily be adjusted and they are noise-free. They are therefore widely used in mats and beds, bed mattresses, electric quilts and blankets, and heating devices for residential use in apartments, general residential dwellings, etc. Moreover, they are also used in heaters for commercial buildings such as offices and stores, industrial heaters for workshops, warehouses, and barracks, and in various other heaters for industrial use, agricultural equipment such as greenhouses and drying systems for agricultural products, and various anti-freezing systems, such as devices for melting snow and prevention of freezing in streets and parking structures. They also have applications for recreational use, protection against cold, household electrical appliances, devices for preventing steam formation on mirrors and glass, health care, animal husbandry, etc.
FIG. 1 is a diagram showing the structure of a plate-type heater according to the prior art. Referring to FIG. 1, the heater essentially consists of multiple ladder-shaped heating lines (11) configured at regular intervals by means of which heating takes place (11). Current-carrying films (12) at either end of the heating lines (11) supply electricity, and transparent film (13) covers all of the heating lines (11) and the current-carrying films (12). In this case, the transparent film (13) is configured in such a way as to cover both the top and bottom parts of the heating lines (11) and the current-carrying film (12).
In the prior art device of FIG. 1, the heating lines (11) are made of carbon, and the current-carrying film (12) is provided in the form of a thin film made of copper or silver. The current-carrying film (12) and heating lines (11) are attached to each other using a conductive adhesive. The transparent film (13) is made of polyethylene (PET).
The manufacturing method of the plate-type heater shown in FIG. 1 is as follows.
First, a printer using conductive ink (the heating material) is used to print the heating lines (11), which are configured in a ladder pattern, on the transparent PET film.
Next, a conductive adhesive is used to attach the thin current-carrying film (12) made of copper or silver in such a way that the ends of the adjacent heating lines (11) are connected.
After this, a transparent film (13) is attached to the surface of the heating lines (11) and the current-carrying film (12) using a dry lamination method, specifically an adhesion-bonding method.
In the embodiment of the plate-type heater shown in FIG. 1, the heater is configured in such a way that heat is generated by the heating lines (11) configured in a ladder pattern. However, the plate-type heaters of prior art essentially have the form of line-type heaters, rather than plate-type heaters that provide all-surface heating. Specifically, heat is generated only in heating lines (11) to which heating material is applied, rather than generating heat throughout the entire surface of the heater.
Therefore, heaters in which heat is generated only in the heating lines (11) have the drawback of a sharply decreased heating effect.
Moreover, in the prior art, because of limitations on the electrical resistor itself in the current-carrying film and concerns about the phenomenon of rapid carbonization of the conductive adhesive used in the current-carrying film (12), it has not been possible to generate temperatures of 50° C. or above in the heating areas or to use such heating devices for long periods. Accordingly, in heaters of the prior art, it is preferable to use thicker wire cut to sections of approximately 1 meter or less, connected by soldering or adhesion in order to connect the heating elements to one another.
In the prior art, moreover, as conduction of electricity and heating were only possible in the areas on which the heating elements were printed, it was necessary to generate relatively high temperatures to transmit heat throughout the entire device, resulting in overloading of the current-carrying areas and the current-carrying film. Accordingly, because of the phenomenon of carbonization of the conductive adhesive used on the current-carrying film, there is a rapid decrease in functioning and there is a high risk of fire resulting from heating of the current-carrying film or conductive printed component.
Moreover, in the prior art, connection must be carried out using thick wires cut to specified lengths (approximately 40 cm-100 cm) or more, which makes connection extremely complex in large-area construction projects, such as laying tile on cement, thus requiring a great deal of manpower.
In the prior art, moreover, as far infrared rays are emitted only in the conductive printed areas, the actual amount of radiation with respect to the entire area to be heated is reduced by half. When the method of prior art is used as is, as the areas in which heat is, and is not, generated are clearly separated, this makes uniform heating unachievable, and it is therefore necessary to cover the heating element with a thermal conductor that can reliably conduct heat. Also, as there is no way to process the induced current generated on the heating element, the problem of damage caused by static electricity must be tolerated. In addition, as the current-carrying plate is large in area, it generates a relatively large amount of electromagnetic waves.
Finally, attempts to fix the current-carrying film in place using an adhesive, require using a film that is as thick as possible, because of this adhesion.